Space reveals a mossy secret

By
Robert C. Cowen /
February 10, 2005

Twenty-first century botany is surprising scientists with unexpected insights into plants they thought they knew fully - like roof moss. Thanks partly to a space shuttle experiment that survived the Columbia disaster, the humble moss has displayed a hidden talent in space. While most plants grow in haphazard disoriented ways when they lack gravity's clues, roof moss appears to have an inner guidance system that causes it to grow in an orderly fashion. Instead of looking like, well, moss, it grew in a distinct clockwise spiral.

This growth pattern is seen only in the absence of gravity - and presented a puzzle for scientists.

Of course, roof moss (Ceratodon purpureus) is a bit of a maverick even on Earth, he notes. In most plants, gravity guides the growth of roots and stems, because many of their cells respond to gravity. With roof moss, just a single cell at the ends of chains of cells senses gravity and responds. The result is that, in the dark underground, the moss grows straight up, away from the center of Earth. When it emerges above ground, light then orients its growth to form familiar mossy structures.

It's different in space. Weightless moss first grows outward like spokes in a wheel. Then these arc to form spiral patterns.

Dr. Sack and his colleagues first flew their moss experiment on Columbia in 1997. They had a second experiment on the spacecraft's final mission. Astronauts had secured the samples before Columbia broke up on reentry. The hardware holding the samples fell to the ground. Of 87 samples, 11 were usable for the research.

The research team explains in the online journal Planta that they have enough data to show the unexpected growth pattern is normal for the plant, not a freak occurrence. Sack speculates that it may be a kind of primitive growth pattern "that later became masked when moss evolved the ability to respond to gravity."

Using such modern tools as a weightless environment, botanists are finding unsuspected properties in plants that have been studied for centuries.

For example: How do flowers create essential oils used in perfumes and other commercially valuable products?

Scientists have long known that plants use two different sets of processes - called biochemical pathways - to make thousands of compounds, including the oils. Each pathway operates in its own separate compartment inside a typical plant cell. Botanists have assumed that each of these miniature chemical factories made its own raw materials. But in snapdragons, one of these units produces all the raw materials for both chemical factories, say researchers at Purdue University in West Lafayette, Ind.

"We never expected to find this," says Natalia Dudareva, who leads the research team. It suggests that, while plants have two chemical pathways to make materials, one of them is not needed. It raises the question of why evolution did not eliminate it. Professor Dudareva also notes that having to work with only one set of chemical processes will make it easier to engineer plants to make more of certain desired products such as essential oils.

Stay tuned for the practical applications that may surprise the rest of us.